Liquid-conductor pump



i conductor.

Patented Feb. 28, 1928.

UNITED STATES KENNETH T. BAINBRIDGE, OF NEW YORK; N.'Y., ASSIGNOB TO GENERAL E LECTBI COMPANY, A CORPORATION OF NEW YORK. y

LIQUID-CONDUCTOR PUMP.

' Application filed May 28,

My invention relatesv to liquidconductor pumps in which the pinch effect produced in a liquid conductor of electric current is utilized in a novel manner to move the 6 liquid or to create a pressure therein.

It is well known that when an electric current flows in a conductor a magnetic field is set up around the'conductor and there is also a magnetic field in the interior of the The interior magnetic field is proportional to the current and inversely proportional to the distance from the axis in the case ofa cylindrical conductor. It is seen that in the interior of the conductor there is a current flowing and a magnetic field so disposed that it results inforces which tend to reduce the cross section of the conductor, and gives rise to what is known as the pinch effect. By properly arranging matters the pinch effect in the liquid conductor may vary so as to create pressure differences and a tendency of the liquid to flow in a manner tending to equalize these pressure differences. One application of this principle is found in the mercury ammeter described in the Standard Handbook of Electrical Engineers, third edition, page 92. No extensive utilization of this principle has been made heretofore because of the very low electrical efficiency realized. Thus the ammeter above referred to requires a very heavy current toproduce a measurable,

pressure difference and is not suitable for measuring currents below 200 amperes. 86 From a purely mechanical standpoint the device would make a very desirable form of pump because it has no'moving part.

It. is the object of my invention to provide such a pump having an electrical efficiency sufliciently high to make it attractive for many applications. a

In carrying my invention into effect I greatly increase the pinch effect for a given current by providing a low reluctance magnetic path for intensifying the interior flux of the conductor. In the preferred arrangement of my invention the reluctance of the flux path is so arranged that the flux lines which are produced solely by the current flowing in the liquid conductor may be said to be eccentric with respect to the conductor, thereby creating a pressure toward one side which is therefore made the outlet of the pump in the manner hereinafter explained in detail.

, electric conductors which may comprise two rent flow and 1926. Serial No. 112,406.

The features of my invention which are believed to be novel and patentable willbe pointed out in the claims ap ended hereto. For a better understanding 0 my invention reference is made in the following description to the accompanying drawing'in' which Flg. 1 represents a cross-section, through a. preferred form, of apump built in accordance with my invention; Fig. 2 is a plan view of the central magnetic plate of the deviceiin which characteristic flux'lines have been represented; Fig. 3 represents a crosssection of the pump taken at right angles to the view shown in Fig; '1 and online 33 thereof; Fig. 4 is a perspectivefview of the pump built as an integral pa'rt of' a, trans former particularly designed to furnishthe electric current for operating the pum Fig. 5 represents curves characteristic of tile pump operation; and Figs. 6 and 7 are views. of an iron plate for eliminating the bend in the pump outlet. V i j i A cross-section of a simple form of pump is shown in Fig. 1. 10 and 11 represent two fiat copper plates. These plates are sepa rated by a third plate 12 of magnetic material such as iron. A thin la er of insulation is provided between the lIOIl and cop er at one or both surfaces. The iron plate A is slotted as shown at 13 in Figs. 2 and 3 from one edge toward the other. When these plates are assembled as shown in Figs. 1 and 3, the slot in the iron plate forms a, conduit which communicates with an outlet opening 14 through the copper plate 11 at" the inner end of the slot 13. The edges of the iron slot are insulated but the surfaces 7 of the cop er plates adjacent the slot are not. Suita le inlet and outletlpipes 15 and 16 are provided for the conduit thus formed. Now if a liquid conductor such, as mercury is allowed to fill this slot. and the two copper plates are connected across any suitable source of electric current, such as is lofi indicated. at 17, a current will flow from one plate to the other through the liquid conductor in the conduit formed in the non slot 13, as indicated by the arrows in Fig; 3.- The flow of current sets up a magnetic 10E flux across the liquid conductor at substantially right an les to the direction of curdue to the nature of the'flux path formed by the slotted plate 12 these flux lines take the eccentric form indicated 11! direction with the reversal of the current,

b the closed lines in Fig. 2. i It isseen that tllelocal magnetic flux is not allowed to scatter ence of the iron and passes normal] .aeross the conductor and completes its ath by traversing the iron at the inner en of the slot. Thus we have a concentrated a'cross and throu h the liquid conductor.

Disregardin Eor the moment any disturbance whic i might be produced by eddy current phenomena when the mercury is the intensity of this field varies directly with the distance from the inner end of the slot and the streiwth of the current and inversely as the width of the slot. It will be seen that the density of the transverse flux at any point in theslot lSPI'llCtlcally determined total current flowing intheslot between the point considered and the inner end of the slot, and is thus a maximum atthe inletend of the slot and zero at the extreme outlet end-of the slot. As this flux slot and the direction of asses normally across the currentflow is substantially or actually perndicularto this ma netic field, forces result on the liquidcon uctor which manifest themselves as [hydrod 'namic pressure at the inneror outletend o the slot, which makes of this device a liquid conductorpumpot remarkable efiicienc as compared to prior arrangements, utilizing the so-called pinch efiect a l A number of practical considerations enterinto the proper design of such a pump. The firstconsideration is the requirement of a heavy current of low volta e. This current may be either direct or a ternating. If direct, the flux lines about the liquid conductor will always be in one direction, and

if alternating, the flux lines will reverse in but the pressure will always be in thesame direction. i

Fi .4 shows one practical embodiment of the invention where the liquid conductor and the communicating electrodes are contained in the secondary circuit of a transformer. 17 re resents the prnnaryjwmding of the trans ormer made up of a number of turns. 18 represents the magnetic core of the transformer and 19 a. single turn secformer can only ondarv winding. This secondary winding is virtua ly a short-circuited secondary made up of the U-shaped conductor 20 and a unit substantially similar to that shown in Fig. 1 comprising the two copper plates 10 and 11 separated byfthe slotted iron plate 12.

The iron plate is insulated from the circuit so that the secondary current of the transflow through "the liquid conductor contained in the conduit formed in the iron late. If a 5 ampere turn primary win ing is used approximately 250 amperes will flow in the secondary circuit.

but is concentrated due to the presmagnetic field v the slot width and the the device independent of temperature changes. The temperature coefficient of mercury is very low as compared to copper and since the mercury makes up the greater part of the resistance of the secondary cir' cuit, the temperature coefiicient of the combined circuitwill always be low. However, if desired, one of the plates 10 or 11 may be made of a conducting material having a high negative temperature eoeflicient of resistance and of such ohmic resistance as to make the resistance of the circuit indepcndent of temperature changes. If the )ump is to produce a. flow of mercury as istinguished from maintaining a certain pressure with little flow and is to be inde endent of temperature changes, attention SlOllld also be given to the fact that the viscosity of mercury decreases with temperature rise and consequently Wlll flow easier through the pump circuit as the temperature increases. This may also be taken care of in-the proper design of the secondary circuit such that the various changes due to temperature willbalance each other leaving the operation of the device independent of temperature changes if that is'desired. a

In'order to provide a good contact between the copper and mercury and not allow the mercur to amal amate with the copper, the latter is preferably coated with, a surface that does not amalgamate but still presents a goodcontact, or a contact which is wet by the mercury. A flash of platinum on the copper surface normally in contact with the mercury will prevent amalgamation and present a perfect contact between the cop er and mercury. Low permeability steel is :fiso satisfactory forthis coating. a

For the insulation between the copper and iron plates, sheets of mica cut the same size as the iron plate and attached thereto b temperature resisting enamel may be usedl To insulate the iron fromthe mercury the slot may be coated by a, suitable enamel.

When thus assembled the device should be thoroughly baked so that no bubbleswill develop later when in use. The pump circuit should of course have as few sharp turns and restrictions as possible. I The proper shapin of the outlet, which should be in general 0 larger area than the 'slotfitself, should be such as to offer the least resistance to the flow therethrough. To eliminate alibe nd at the outlet end of the slot the outlet may be made straight through the iron plate increased at this point to retain the low reluctance flux path asindicatedin Figs. .6

l -'and7.- 1 Figs. 6 and 7 correspond to the views of the :ironvplate shown inFigs. 2 and 1 reformer core and the iron platew12 1nay be of spectively. "'lVhen mercury flows through the slot, a voltage is inducedzin the mercury opposing the flow :of current. 9 i In such. cases it may be advisable reshape the slot such that thelinducedJvoltage alongthe slot is the same at all pointsl- This can be accomplished: bydesigningthe slot suchthat Be is a constant where Bequ-als the flux density 'crossingthe slot at. any point-and 2) equals the velocityofflowat the-same point. WVhen this isdone there are no local circulating currents in the copper and mercury that flux distributionlfi v The flux density of the transformer core is low and the core may be ofsmall, area. The core loss will be negligible, Thetranswould reduce the efficiency and disturb the laminated material in accordance withgood practicei The devicewill be 1 substantially independent ofwfrequencyh changes if the magnetic circuits are operated below saturation. q 1

In Fig. 4. Ihave shown variouscurves obtamed, by plotting-thestaticpressure head in centimeters of mercury against the corretainable withl'a device of the samedimensions as. thati used for .the test curves, and curve F represents the calculated theoretical pressure obtainable at the center of a circular mercury conductor of the same area as that used in the tests but without the use of iron to concentrate the flux.

The mathematical calculations for obtaining curves E and F are somewhat involved and are not reproduced here. In general the increase in pressure for my design of pump over the ordinary pinch eflect'is theoretically w where d equals the effective length of the slot and w the width. In general 5 should be large for high pressure. In the apparatus built and tested it was calculated vices utilizin the f inch effect. When a higher pressure is desired thanthat which is practicable to obtain by a zsingle unit or pump, such as has been described, twoor more such units may obviously be connected in series. p c lhere are many applications where such a pump may be UtlllZOCl. ,The fact that there are no moving parts such as valves, pistons, l)til1 l11gS,,6tG-., makes this type of pum very attractive. No lubrication is require There is no wear of rubbing parts; There is -no noise. The action may be made-independent of temperature and frequency variations so asto make the pump suitablefor accurate relay purposes. Ordinarily a liquid pump' requires two elements, the pump itself, and some kind of a motor for driving the pump. In the present case the two are combined in a single unit in a very simple and compact manner, it being required however that the liquid shall be an electricconductor. N

.In accordance with 'the'provisions of .the patent statutes, 1 have describedthe principle of: operation of my inventiomtogether witlithe apparatus which I now consider to represent thebest embodiment thereof; but I desire to have it understood that the apparatus shown and. described is only illustrative and that the invention may, out by other means. Y I I lVhat I claim as new, and: desire to secure by Letters Patent of the United States,

1. A fluid conductor pump comprisin'g an electric circu t having-a portion thereof made up of a fluid conductor a conduit with inlet and outlet openings for such fluid concluctor, and magnetic means conductively excluded from said electric circuit and magnet zed solely by the fiuxset up by the current flowingv in said conductor for directing the flux, due to current flowing in said con- I carried ductor, through and about said conductor so as to produce points of different flux intensity therein at the inletiand outlet of said conduit. a

2. A liquid conductor pump comprising an electric circuit having a portion thereof made up of a-liquid conductor, a conduit for such liquid conductor, magnetic means magnetized solely by the flux set up by the cur rent flowing in said conductor and positioned closely adjacent the liquid conductor portion of said electric circuit, but not conductively included therein, for producing a low reluctance flux path guiding the flux produced by the current flowing in said conductor, across said conduit at substantially right angles to the direction of current flow therethrough and with varying intensity at different points therein, and inlet and outlet openings in said' conduit at points of different flux intensity therein.

3. A liquid conductor pump comprising an by the current uid conductor, an inlet duit and an outlet for said conduit at a point said lltglidconductor .su'ch conduit of substantially of minimum fluu intensity of said conduit.

4. A liquid conductor pump comprising an electric circuit" having a portion thereof made upof aliquid conductor, aconduit for said liquid conductor, magnetic means magnetized solely by the 'flux set up by the curu said conductor and insulated rent flowin from said fe ectriccircuift to reducing alow reluctzlncefflux fpath partial y surrounding that the flux produced y -current flow in in said conductor variesinintensit :at'di erent points in said conductor and in et and outlet openirhgs into suidconduit at poi ts of diflerent ux; intensity therein,

5. A fluid conductor pump com rising a section, two opposite sides of which are formed of electric conductors and the other from a substantially structure, said magnetic structure 'bytheflux set up bythe sides of which but insulated etic are enclosed by;

ll-shaped ma magnetized solely current flowing n said conductor, an inlet for-said condnitat the open endof said U- uid conductor a conduit for outlet openings for said liquid conductor,

rectangu ar cross sity coeflicientiof said electric circuit being such sllu'sed nmgneticstructure, an outlet ior said COD structure, a liquidconductor in said conduit, anelectric circuit and connections for including said two eiectric conductors and said liquidm series relation in saidcircuit.

6. Aliquid conductor pump comprising an electric circuit formed by substantially a short-circuited secondary of a transformer, a portion of said circuitbeingimadeflu'p of a liquid conductor, a conduit with inlet and l and magnetic means magnetized solely by the flux set up b the current flowing in said conductor for irecting the flux reduced by the current fiowingun said con uctor, so

as to produce points of difierentu flux intensity in said liquid'conductor at the inlet and outlet points. I

a 7 A fl id conductor pump comprisingani electric circuit having a portion thereof madeup of a fluid con ctor, a conduithwith inlet and outlet openingsiforsaid fluid conductor, and magnetic means magne solely by the flux setup by the current flowin in said conductor and insulated from said electric circuit for idirectingthe flux, due to current-flowing insaidconductor, so as to produce points-of different flux intenin the conductor at the inlet and outlet of said"c0nduit, the combined tem rature as to make the operation of 88161 pump substantially independent a of temperature changes: i y it y w In witness whereof, I have hereunto set my hand this 26th da of Ma "1926.

BAI BRIDGE.

uit atthe closed end of said magnetic 40 

